Tonga Earthquake and Tsunami Warning: Lessons Need to be Learned

This morning at 4:26:40 Tonga time (2006 May 3 15:26:40 UTC), an earthquake struck the Ha'apai Group of Tonga. The Pacific Tsunami Warning Centre issued a Regional Tsunami Warning.

The resultant misreporting in the global press and the reaction (or lack thereof) of various civil defence authorities throughout the region clearly reinforces the case that the region is not prepared for a major tsunami.

First allow the facts to be clearly stated as they are now known:

Current report from USGS

Magnitude 7.9 (Major)
Date-Time Wednesday, May 3, 2006 at 15:26:40 (UTC) = Coordinated Universal Time
Thursday, May 4, 2006 at 4:26:40 AM = local time at epicenter
Location 20.088°S, 174.219°W
Depth 55 km (34.2 miles) set by location program
Region TONGA

APCEDI can now provide a more accurate report from the area. The earthquake was felt very strongly throughout the Ha'pai Group. No one in the Ha'apai Group has been reported injured or killed. Minor cracking resulted to buildings in Pangai including the hospital and some main resort buildings. Minor cracking of roads on Lifuka was also reported. The earthquake was also felt strongly throughout the Vava'u Group to the north and across the southern islands of Tonga including Nuku'alofa and 'Eua. The only injury currently being reported from Nuku'alofa is to a Korean student who jumped out of his hotel window during the quake. The electric grid across Nuku'alofa also cut out for a short time.
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The news media have consistently been misreporting the event. First nearly all of them have put the quake's depth at 16 km and the magnitude variously at 8.1, 8.0 and 7.8. This includes CNN, BBC and the ABC and a host of minor publications following their lead. There is a great deal of difference between 16 km and 55 km in depth when it comes to the ability of a 7.8-8.1 earthquake to generate a tsunami.

What the media does not seem to appreciate is that the USGS earthquake reports are preliminary data generated by machines. Upon review by seismologists, this data regularly changes. Occasionally it changes significantly. While the various values of the size on the magnitude can be accounted by the change in review of the USGS, there is nothing to account for the incorrect reporting of the earthquake's depth. This is simply shoddy and irresponsible reporting all around. News media must constantly check the USGS website to ensure that the most current data is being used.

The next major error was the media's reporting about the location of Tonga. The location of the quake was in the Ha'apai Group off the island of Lifuka about 20 km southeast of the resort town of Pangai. This is over 160 kms from Nuku'alofa. However news media had the earthquake is various places such as "off the northeast coast of Tonga", "near the island of Tonga" and "near the island's capital". These geographical terms are not useful in any way. This is very similar to reporting on the islands during cyclones. If the media is going to report on these islands, then they must clearly understand their geography and give locations that are coherent and useful. Doing otherwise is again irresponsible and can create confusion.

Then several news media including the BBC started reporting about evacuations "across New Zealand" due to an actual tsunami. People awake in the USA and Europe started calling relatives in New Zealand, Samoa and Fiji, and sporadic evacuations started occurring throughout coastal areas in many places particularly in New Zealand and around the Gisborne area. New Zealand citizens who tried to get information from the police and civil authorities at this early hour of the morning could not get any useful information.

Two useful news stories on the New Zealand situation are New Zealand Press and Stuff.co

What is clear is that between the mainstream media and civil authorities there was a major disconnect. The media did not do a good job of clearly reporting the situation or the exact threat, and as outlined below the civil authorities were simply not prepared and caught largely off guard.
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Immediately after the quake the Pacific Tsunami Warning Center issued a tsunami warning for the Region. However, few people in the region were aware of this in a timely fashion. The French Government subsequently sent out a warning which likewise seem to likewise disappear in the ether. Where the warning was received in a timely fashion it is unclear in many cases if it triggered any major follow-up procedures. The following is an rough examination of the island areas that would be most at threat from a tsunami generated by a quake in this region, and what happened there during this episode.

Tonga: The island groups of Tonga were most at threat as any tsunami would have obviously reached them first. However, apparently due to a breakdown in an internal communications' system, the Tonga authorities received no warning at all. Also there seemed to be no internal mechanism for warning. It is unlikely that a global warning no matter how quick could have reached Ha'apai Group before a tsunami would have struck especially the front islands like Lifuka. However, a timely warning could have been critical to the other islands. Authorities in Tonga, New Zealand and Australia must carefully study exactly what went wrong here, and make sure that it is never repeated.

Niue and the Cook Islands: If one studies the open ocean topography, the epicentral area of the quake and look at linear distances, it would have been Niue and the Cook Islands that would likely have been next in line after Tonga. However, they seemed to have fallen off everyone's radars. If a major tsunami had been generated, it would have rolled right across Niue and Rarotonga and the western most Cooks virtually unattenuated by any other island group. This raises a critical issue. Any tsunami that is likely to threaten Niue and the Cooks has a high probability of also threatening New Zealand. As was clearly illustrated, New Zealand is not well prepared for such a threat and should a major tsunami threaten to hit New Zealand, their territories of the Cook Islands and Niue will be the last thing that New Zealand will be worrying about. Thus, the Cook Islands and Niue likely need to separate any reliance on New Zealand for a tsunami warning and be self-sufficient in their own right. Authorities in Niue, the Cooks, New Zealand and Australia must carefully study this situation and why Niue and the Cook Islands were not adequately warned in this instance.

Addendum: The New Zealand Ministry of Civil Defence and Emergency Management has sent me an email clarifying that in fact the Cook Islands Tsunami Warning System currently in place has already been designed to be completely separate and stand alone, similar to those in other independent island states. They have also provided assurances that tsunami-related communication systems will be the subject of much scrutiny in the up-coming tsunami exercise and on-going disaster preparedness reviews.

New Zealand:The situation here has been described in detail in the above articles, with many other articles likely to be out in the next few days. Now that the Minister for Civil Defence, Rick Barker, has admitted that the official response to this tsunami warning was not up to scratch, there will likely be a major review of these procedures.

Fiji: Fiji seems to have been better prepared than most. They did receive the warning immediately, and at least were getting some news out in the Suva area. However, given the topography of the quake to the east of Tonga's Ha'apai Group, these islands would have greatly attenuated any tsunami towards to the northwest, and Fiji would have likely been spared in any case. The Lau Group of Fiji would have only served to further attenuate any major tsunami hitting Fiji from this area. It seemed however that the warning was never received by any authorities in the Lau Group until the threat would have been well over. Authorities in the Fiji, New Zealand and Australia must carefully study this situation and make sure that the outer islands of Fiji are adequately prepared.

Samoa and American Samoa:Samoa and American Samoa like Fiji did receive and register the warning immediately. However, it is unclear what steps, if any were taken by authorities.

There is a major 28-nation Pacific trial of the new tsunami warning system. Part of this trial needs to be a clear review of what happened today, and how to make sure that such errors and miscommunications do not happen in the future. It is critical that lessons learned from today be incorporated into building a solid tsunami warning system for the Region.


Kevin Vang
APCEDI Coordinator
http://www.afap.org/apcedi/

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